The present disclosure relates generally to drill bits for drilling a wellbore. The present disclosure is generally directed to seals, such as dynamic seals for roller cone drill bits, and, for example, a packing resistant radial lip seal that may be used on a relatively large diameter roller cone drill bit.
Sealed and lubricated earth boring drill bits have been in use in the oil well drilling industry for several decades. In order to help reduce the friction at the radial seal interface, a means of enhancing lubrication by trapping it at the sealing interface may be provided, as described for example in U.S. Pat. No. 4,619,534. In these designs, however, at a given operating RPM, as the diameter of the drill bit increases, the surface speed of the seal against its seal land may also increase such that, at the very large bit diameters common for motor bits, the sealing interface may be sliding against the seal land at quite high rates. It may also be important that a radial lip seal does not slide within its seal groove in order to maintain stability in operation. Otherwise, this can lead to rapid heating and early failure, especially if the seal is deformed with cutting packing into the seal groove. Therefore, a reliable way to lock the radial seal in place in the cutter groove may be useful. Disclosed herein is a device for hydrostatically locking a radial seal in place in the cutter of a rolling cutter drill bit. This device may be applicable to rolling cutter drill bits that drill boreholes 8-½ inches (21.59 cm) in diameter and to rolling cutter drill bits that drill large diameter boreholes of 12-¼ inches (31.11 cm) and larger in diameter.
Sealing large diameter bits may be challenging when providing radial cross-section elastomeric seals for drill bits of very large borehole diameters (e.g., about 12-¼ inches (31.11 cm) or greater). A 12¼ inch (31.11 cm) drill bit operating at 250 rpm may have a surface speed at the seal land of 3450 inches (87.6 m) per minute. Seal failures at the very high surface speeds may lead to new seal designs with reduced operating friction, as described for example in commonly owned U.S. Pat. No. 7,036,613, the entire contents of which are hereby incorporated by reference herein. This design may be intended for increasing drilling rates of penetration in some drilling application. However, in some cases, the flushing system intended to carry the drilled earth to the surface may become overwhelmed to the point that the drill cuttings become packed around the drill bit and pack into a seal groove area of the drill bit.